| Message ID | 20240109230250.424295-12-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/pmu: selftests: Fixes and new tests | expand |
On 1/10/2024 7:02 AM, Sean Christopherson wrote: > Explicitly check for attempts to read unsupported PMC types instead of > letting the bounds check fail. Functionally, letting the check fail is > ok, but it's unnecessarily subtle and does a poor job of documenting the > architectural behavior that KVM is emulating. > > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/vmx/pmu_intel.c | 21 +++++++++++++++------ > 1 file changed, 15 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c > index c37dd3aa056b..b41bdb0a0995 100644 > --- a/arch/x86/kvm/vmx/pmu_intel.c > +++ b/arch/x86/kvm/vmx/pmu_intel.c > @@ -26,6 +26,7 @@ > * further confuse things, non-architectural PMUs use bit 31 as a flag for > * "fast" reads, whereas the "type" is an explicit value. > */ > +#define INTEL_RDPMC_GP 0 > #define INTEL_RDPMC_FIXED INTEL_PMC_FIXED_RDPMC_BASE > > #define INTEL_RDPMC_TYPE_MASK GENMASK(31, 16) > @@ -89,21 +90,29 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu, > return NULL; > > /* > - * Fixed PMCs are supported on all architectural PMUs. Note, KVM only > - * emulates fixed PMCs for PMU v2+, but the flag itself is still valid, > - * i.e. let RDPMC fail due to accessing a non-existent counter. > + * General Purpose (GP) PMCs are supported on all PMUs, and fixed PMCs > + * are supported on all architectural PMUs, i.e. on all virtual PMUs > + * supported by KVM. Note, KVM only emulates fixed PMCs for PMU v2+, > + * but the type itself is still valid, i.e. let RDPMC fail due to > + * accessing a non-existent counter. Reject attempts to read all other > + * types, which are unknown/unsupported. > */ > - idx &= ~INTEL_RDPMC_FIXED; > - if (type == INTEL_RDPMC_FIXED) { > + switch (type) { > + case INTEL_RDPMC_FIXED: > counters = pmu->fixed_counters; > num_counters = pmu->nr_arch_fixed_counters; > bitmask = pmu->counter_bitmask[KVM_PMC_FIXED]; > - } else { > + break; > + case INTEL_RDPMC_GP: > counters = pmu->gp_counters; > num_counters = pmu->nr_arch_gp_counters; > bitmask = pmu->counter_bitmask[KVM_PMC_GP]; > + break; > + default: > + return NULL; > } > > + idx &= INTEL_RDPMC_INDEX_MASK; > if (idx >= num_counters) > return NULL; > Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index c37dd3aa056b..b41bdb0a0995 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -26,6 +26,7 @@ * further confuse things, non-architectural PMUs use bit 31 as a flag for * "fast" reads, whereas the "type" is an explicit value. */ +#define INTEL_RDPMC_GP 0 #define INTEL_RDPMC_FIXED INTEL_PMC_FIXED_RDPMC_BASE #define INTEL_RDPMC_TYPE_MASK GENMASK(31, 16) @@ -89,21 +90,29 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu, return NULL; /* - * Fixed PMCs are supported on all architectural PMUs. Note, KVM only - * emulates fixed PMCs for PMU v2+, but the flag itself is still valid, - * i.e. let RDPMC fail due to accessing a non-existent counter. + * General Purpose (GP) PMCs are supported on all PMUs, and fixed PMCs + * are supported on all architectural PMUs, i.e. on all virtual PMUs + * supported by KVM. Note, KVM only emulates fixed PMCs for PMU v2+, + * but the type itself is still valid, i.e. let RDPMC fail due to + * accessing a non-existent counter. Reject attempts to read all other + * types, which are unknown/unsupported. */ - idx &= ~INTEL_RDPMC_FIXED; - if (type == INTEL_RDPMC_FIXED) { + switch (type) { + case INTEL_RDPMC_FIXED: counters = pmu->fixed_counters; num_counters = pmu->nr_arch_fixed_counters; bitmask = pmu->counter_bitmask[KVM_PMC_FIXED]; - } else { + break; + case INTEL_RDPMC_GP: counters = pmu->gp_counters; num_counters = pmu->nr_arch_gp_counters; bitmask = pmu->counter_bitmask[KVM_PMC_GP]; + break; + default: + return NULL; } + idx &= INTEL_RDPMC_INDEX_MASK; if (idx >= num_counters) return NULL;
Explicitly check for attempts to read unsupported PMC types instead of letting the bounds check fail. Functionally, letting the check fail is ok, but it's unnecessarily subtle and does a poor job of documenting the architectural behavior that KVM is emulating. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/vmx/pmu_intel.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)